Process of recovering sugar.



out of its impure solutions the property of ful Improvement-sin Processes of Recovering V UNlTED STA-r1 31 PATENT" DEFICE.

ALFRED WOl-lL, or CIIARLOTTYENBQURQYAND ALEXANDER KoIILnErr,

or BERLIN,

GERMANY.

' PROCESSOF' REoovERiNc SUGARQ $PEGIFICATION forming part of Letters Eatent No. 95,702, dated March 18, ieoa. I

Applicationifiled October 20, 1900. I

To all whom; it may concern:

' Be it known that we, ALFRED W'OHL, Pln D.', residing in Oharlottenburg,'near Berlin, and ALEX NDER KOLLREPP,'Ph. D., residing in Berlin, Germany, citizens'of the Empire'of Germany, have invented certain new ancluse- Sugar, of which the following is a specification. g

This invention relates,toimprovements in that particular method of sugar-manufacture in which is employed for separatingthe sugar certain chemical compounds of combining with the sugar, forming a sucrate, sai'd sucrate beingthen removed from the solution and further treated for obtaining the sugar therefrom. Lead oxid and lead carbonate are substances commonly employed for this pur pose. Recovery of the sugar from the lead sucrateis commonlyeffected bywhatis known as the saturation method, in which the lead sucrate in aqueous solution is subjected to contact with carbonic-acid gas, whereby lead carbonate is formed and sugar set free. When for carrying on the process of sugar-manufacturing according to this method lead carbonate is employed, said lead carbonate is not commonly employed alone, but in connection with an alkali solution or lye, such as a solution of potassium hydrate, (caustic potash.) The basic carbonate of lead is usually employed. Basic carbonate of lead also is the product of the saturation stage, and it is common to use the carbonate produced by the saturation stage of a preceding run for mixing with the sugar solution fora subsequent run, thus forming a cycle process. Owing to other features of the process, it is desirable that this alkali-lye should be dilute, and it is common to use a lye so dilute that although binding of almost all the sugar takes place,still all the sugar is not entirely bound 2'. e., converted into lead sucrate. This difliculty may be overcome, however, by employing instead of the basic carbonate a carbonate more highly (preferably completely) saturated with carbonic acid-for example, the normal carbonate. When this substance is used, the binding of the sugar is complete, even though the alkali-lye be of somewhat Serial No- 33.774. (No specimens.)

greater than the customary dilution. It is possible to produce this normal carbonate in This is attained by continuing the saturation with carbonic-acid gas for a' much longer time -the saturation stage instead of'producing the basic carbonate, which is the usual result.

than usual--in other \vords,'saturating until" theprecipitate shows an acid reaction. This,

however, is very deleterious to the sugar, for

the reason that non-saccharine 'matters,-rin

particular alkali salts'in the form of lead d'ou ble salts, are formed, which dissolvein the bonate of lead produced by this method'is not as pure as is-desirable; and the impurities accumulated in the same after a fewruns render it unfit for use in the cycle process.

The object of this invention is to provide a process by which normal carbonate of lead and sugar, both containing a less quantity of impurities,'may be obtained from the lead-v sucrate solution; and for this purpose the in'-' vention consists in the steps of expressing the lye from a mixture of alkali-lye and lead sucrate, treating the sucrate with a warm washlye, washing the sucrate, and saturating the same with carbonic acid.

The following example will indicate clearly the steps of the new process. Into a suitable vessel provided with an agitator are introduced five hundred kilograms molasses 01 other sugar solution from which it isdesired to separate the sugar in a pure state, five hundred kilograms strong normal carbonate of lead containing about twenty-five percent.

water, and one hundred and twenty liters crude potash-lye of 1.5 per cent. strength. Twelve hundred liters crude lead sucrate are also introduced, and the mass is agitated for about fifteen minutes and then allowed to crystallization of lead sucrate ensues, the en-' tire mass of sugar in the molasses being completely converted into lead sucrate. By compression of the mass in a filter-press the lye is now expressed from the lead sucrate. Said lye is now heated to 5060 centigrade, subjected to contact with carbonic-acid gas, and filtered. The filtrate, which is free of lead, is evaporated and the residue burned in to crude potash, which is suitable for use in repeating the process. The lead sucrate remains in the press in the form of a pulp. In order to free the same from the small quantity of alkali-lye not expressed, it is necessary to wash it. This lixiviating with water may be accomplished without intermediate treatment of the sucrate; but when this is done the filter cloths become quickly clogged, due to the fact that the wash-water converts a small quantity of lead which is contained in the lye into lead carbonate, and this fills up the interstices of the cloths. This disadvantage is presentwhether lead carbonate or oxid be used as the desaceharification material. The difficulty may, however, be avoided by not lixiviating the sucrate at once, but first subjecting it to treatment with a weak alkalilyefor example, the lye commonly known in this industry as wash-lye. The pulpy sucrate mass is kneaded, mashed, or otherwise thoroughly mixed with a suitable quantity of this lye, preferably in a warm state, and when the mixing is complete is mixed with a further quantity of a still more dilute lye heated to a higher temperature. The heating of the lye causes the greater part of the lead in solution to precipitate in the form of a granular deposit. After the second mixing the sucrate mass may be lixiviated with water in the filter-press without fear of the cloths becoming clogged. After washing, the sucrate is saturated with carbonic acid,which is accomplished by passing carbonic-acid gas through an aqueous solution of the sucrate or otherwise bringing the solution into intimate contact with the gas, whereby the lead sucrate is decomposed, the lead uniting with the carbonic acid and forming basic lead carbonate and the sugar forming with the water a syrup. At the point when the liberation of the sugar is complete carbonation is interrupted and the entire mass filtered. The sugar goes off in a comparatively pure state in the solution and is afterward allowed to crystallize out or is separated out in any wellknown manner. The precipitate remaining behind in the filter contains lead carbonate and impurities. To remove the latter, the precipitate is repeatedly washed. It is then mixed with water in abundance, in which it is held in suspension.

The mixture is then subjected tosaturation with carbonic acid gas. The basic carbonate absorbs under this treatment a further quantity of carbonic acid and is converted into a comparatively pure normal carbonate suitable for use in a subsequent run of the process. It is desirable to add to the mixture of the precipitate and water a small quantity of a suitable acidsuch, for example, as muriatic acid. This addition aids the reaction, and the acid itself acts to reduce the remaining insoluble impurities, such as carbonate of lime, while the highly-saturated carbonate of lead remains unchanged by the acid.

The process above described is also of advantage in that from the normal carbonate produced a superior grade of lead oxid can be obtained in case that substance is used as the desaceharilication material in place of the carbonate itself.

Having thus described our invention, we claim as new and desire to secure by Letters Patent- 1. 'lhe'herein-described process ofreeovering sugar, which consists in expressing the lye from a mixture of alkali lye and lead sucrate, treating the lead sucrate with warm Wash-lye, washing the sucrate and saturating the sucrate with carbonic acid, substantially as set forth.

2. The herein-described process of recoven ing sugar, which consists in expressing the lye from a mixture of alkalilye and lead sucrate, treating the lead sucrate with warm wash-lye, washing the sucrate, saturating the same with carbonic acid, interrupting the saturation when the sugar is entirely liberated, separating the sugar solution from the precipitate, and subjecting the precipitate to additional saturation with carbonic acid, substantially as set forth.

3. The herein-described process of recovering sugar, which consists in expressing the lye from a mixture of alkali lye and lead sucrate, treating the lead sucrate with warm wash-lye, washing the sucrate, saturating the same with carbonic acid, interrupting the saturation when the sugar is entirely liberated, separating the sugar' solution from the precipitate, and subjecting the precipitate in a dilute acid solution to additional saturation with carbonic acid, substantially as set forth.

In testimony that we claim the foregoing as our invention we have signed our names in presence of two subscribing witnesses.

ALFRED WOHL. ALEXANDER KOLLREPP. \Vitnesses:

ERNST voN NIussEN, \VOLDEMAR lIAUPT. 

